Modpack installer should put everything to right place automatically, no need to copy files around. Note that tilesets are not compatible between freeciv versions (except bugfix releases denoted by third number), so to use it in both freeciv-2.4 and freeciv-2.5, you need to install it with both freeciv-2.4 modpack installer (freeciv-modpack) and freeciv-2.5 modpack installer (freeciv-mp-<gui>, where gui is probably "gtk2").